LED lighting has seen increasing use in the past few years. Some of the advantages of LED lighting include much reduced power consumption compared to incandescent or even fluorescent lighting, long life of the LED fixtures, precise control, numerous variations in the color of the light emitted by LED fixtures, and reduced size and weight of the fixtures allowing for greater use in various applications.
Traditional lighting (for example incandescent or fluorescent) uses relatively high voltage AC power, for example, either 120V or 277V AC. Likewise, LED light fixtures may also utilize high voltage AC power, but this “high” voltage is converted to a relatively “low” DC voltage (12-36V DC) to power the LEDs within the fixtures. To generate this DC voltage, it is typical to provide a voltage converter (a step down transformer) within each LED fixture that converts 120V AC into 12-36V DC. However, this configuration undesirably requires the installation AC wiring that meets the electrical code requirements for distribution of 120V AC power to each LED fixture. This makes installation a rather time and labor intensive and must be performed by licensed and qualified personnel. This configuration also requires the use of a converter in each fixture, which is highly inefficient as each converter will waste a large amount of power in heat dissipation.
Some power distribution systems have envisioned using low voltage wiring as opposed to using standard 120V AC power. For example, in the field of computers and telecommunications, Cisco has provided a system that is called Power Over Ethernet (PoE). PoE describes a system which passes both electrical power and data on conductors in a twisted pair Ethernet cable. This allows for a twisted pair cable to provide both electrical power and data to a device. The advantage of this type of system is that it eliminates the higher voltage wiring but instead, uses only class II low voltage wiring for 48V DC. This means that the installation of the wiring does not have to be performed by licensed individuals. Nor does the wiring have to be installed and secured in a highly regulated manner as the fire hazard of class II wiring distributing lower voltage is negligible.
However, a major disadvantage of the PoE system is the lack of precise control of the power distributed over the low voltage wiring. Furthermore, while for computer applications it may be desirable to provide power and data over the same conductors, this configuration limits the amount of power that can be transmitted over the wires and constrains the ability to control power transmitted over such wires. This is true even for Cisco's “new” system Universal Power over Ethernet (UPoE). Therefore, there are severe limitations on the versatility and efficiency of the system as used for both power distribution and data transfer.
Other known systems use passive “polyswitch” MOV devices to regulate power. These passive systems employ varistors, however, these devices do not provide precise control of power and therefore severely limit the amount of power that can effectively be transmitted over the conductors.
It is contemplated that an active power distribution system (as opposed to passive type systems) for controlling over current and voltage would facilitate providing a highly controllable and precise amount of power to be transmitted over low voltage cables. This active type system would allow for the precise setting and control of fault detection and cable protection.